A conventional technology disclosed in JP 2008-250906 A is a technology in which a mobile robot moving autonomously estimates a vehicle position according to amount of movement and, by matching a passage detected by laser scan with map information acquired in advance, performs correction of the estimated vehicle position. The detected passage and the map information are treated as two-dimensional data when viewed in plan, and, when performing matching between them, only data in a predetermined range from a present location are used.
To detect a target, such as a white line and a curb line, and, by matching the detected target with map information, calculate a vehicle position (absolute coordinates on a map) of a vehicle, a reference point for matching the target with the map information is required. For example, when only a white line extending in a straight line is detected, the white line extending in a straight line, in a traveling direction, serves as a reference point in the vehicle width direction but does not serve as a reference point in the traveling direction, and thus matching with the map information cannot be performed accurately in the traveling direction. Therefore, when a configuration in which only target position data in a predetermined range from the present location are retained is employed, there is a possibility that, when, for example, only data relating to a white line extending in a straight line in the predetermined range from the present location are available, no target position data serving as a reference point in the traveling direction are available, which makes it impossible to obtain an accurate vehicle position of the vehicle. However, retaining all the detected target position data is not practical because doing so causes a required storage capacity to be substantial.